【 Weak current College 】 buy hard skills complete guide

In order to meet the network application performance needs of growing, we usually increase the number of the new server, share business, improve system performance, i.e. landscape scale. In fact, you can improve the existing server configuration to improve the overall performance of the server, which is longitudinal extension – because the server part of matching the performance of the server is critical. While the direct purchase of the hard drive to store data is affected the performance of the Server service.

Increasing server performance is to look for restricting server performance bottlenecks. Different application possible bottlenecks is different, some want to focus on processors, memory, and to focus on buying hard disk or network i/o throughput capacity; in that case, in which applications need to focus on the server hard disk bottleneck?

Communication Server (E-mail/messaging/VOD): fast I/O is the key to this type of application, choose the hard disk i/o throughput is the main bottlenecks;

Data warehouse (online transaction processing/data mining): large commercial data storage, cataloging, indexing, data analysis, high speed business computing, and so on, you need to have good network and disk I/O throughput capacity;

Database (ERP/OLTP, etc): the server running the database, you need to have powerful CPU processing power, memory capacity to cache data, at the same time there needs to be very good I/O throughput performance;

Other applications: applications focused on data query and network communication, frequently read and write the hard drive, then choose the hard disk's performance directly affects the overall performance of the server.

Factors influencing purchase hard drive

To purchase the hard disk of the target parameter, first of all it should be mentioned that the hard disk interface standard. Today's mainstream hard drive interface interface has two kinds: EIDE and SCSI, IEEE1394 interface, of course, in addition, the USB interface and FC-al (FibreChannel-ArbitratedLoop) Fibre Channel interface products, but very rare. Now almost all computer-based General UltraDMA/33/66/100 the standard IDE interface hard disk, it has the advantage of being able to offer a lower price, the penetration rate is very high.

At the same time, some low-end server used the IDE hard drive, at present, almost all server Board is integrated with the IDE controller, but in the middle and high-end server is generally used to connect low-speed peripherals IDE optical drive and hard drive generally use SCSI interface standards such as wave yingxin server generally adopts Ultra160SCSI hard drives provide higher disk throughput capacity. SCSI interface hard drive has a very low CPU usage, support more devices and the work of the task under obvious advantages, etc., are better suited for server applications, and of course the SCSI hard drive price is much higher.

However, the optional hard disk data transfer bottleneck of the system lies not in the PCI bus or interface rate, while in the hard disk itself, which is part of the hard disk mechanical and structural design, and many other factors.

Indicators measuring the purchase of hard disk

Measure hard disk performance indicators include:

Spindle speed

Spindle speed is one of the hard disk capacity in addition all indicators, the most notable performance parameters should also determine the hard disk's internal transfer speeds and sustained transfer rate of the first decision factors. Now choose the hard disk rotational speed are 5400rpm, 7200rpm, 10000rpm and 15000rpm. Judging from the present situation, 10000rpm SCSI hard disk with cost-effective advantages, is now mainstream, and hard drive 7200rpm hard drive and the following levels in the phasing out of hard drive market.

Internal transfer rates

The level of internal transfer rate is the evaluation of a purchase hard drive a decisive factor in overall performance. Hard disk data transfer rate is divided into internal and external transfer rate; typically refer to external transfer rates as well as burst data transfer rates (BurstdataTransferRate) or interface transfer rate, measured from the hard disk cache to output data, current Ultra160SCSI technology external transfer rates have reached 160MB/s; internal transfer rate also known as the maximum or minimum sustained rate (SustainedTransferRate) refers to the purchase of hard disk platters read write data speed, now most of the mainstream HDD 30MB/s to 60MB/s. Due to the hard disk's internal transfer rate to less than the external transfer rate, only internal transfer rate can be as real to measure hard drive performance.

Single-disc capacity

In addition to contributions to growth capacity, single-disc capacity of another important significance is to increase purchase hard disk data transfer rate. Single-disc capacity increase thanks to the increase in the number of tracks and track internal linear magnetic density increases. Tracks the number of reducing head seek times of great benefit, because magnet's RADIUS is fixed, tracks the number of means of shortening the distance between the track and heads from one track to another track takes place time will be shortened. This will help to random data transmission speeds increase. And track internal linear magnetic density of growth and drive continuous data transfer speeds are directly linked. Track the increase in linear density allows each track you can store more data on the disc in each circular motion and more data is read from the head to the hard drive's buffer.

Average seek time

Average seek time is the head moves to the data track time, this is a measure of the importance of choosing the hard disk mechanical indicators, usually in 3ms ~ 13ms, recommended average seek time is greater than 8ms SCSI hard drives don't consider. Average seek time and average latency (the decision entirely by speed) together determine the hardSpare head to find clusters of data is located. The time has a direct impact on the hard drive of random data transfer speeds.

Cache

Improve the capacity of the hard disk cache is an increase the overall performance of the purchase of the hard drive. Because hard disk's internal data transfer rate and external transfer speed. So you need to do a cache to speed adapters. The size of the cache duration for hard disk data transfer rate has a great impact. It has a capacity of 4MB 512KB, 2MB, or, even, for 16MB 8MB video capture, video editing, etc. require a large amount of disk input/output, large hard disk cache is the ideal choice.

Selected server hard drive

Know your server to buy hard disk performance indicators, the next natural to choose a suitable for this specific application servers hard drive to improve system performance.

Choosing high performance hard drive

Because SCSI has a CPU utilization is low, the number of tasks associated with operating efficiency, connection equipment, connect the long distance, for most of the server application, it is recommended that you use SCSI hard drive, and the newest Ultra160SCSI controller; for the low-end of a small server applications, can be up to date on your IDE hard disk and controller. Determines the type of interface and the hard disk, will focus on the aforementioned effect drives performance specifications, depending on the speed, single-disc capacity, average seek, cache, and other factors, combined with capital budget, selected price best buy hard disk options.

RAID technology

Redundant disk array and RAID system offers more than the usual disk storage more performance indicators, data integrity, and availability of data, especially in today's hard disk i/o is always lag behind the CPU performance bottlenecks and more prominent, RAID solutions to effectively compensate for this gap.

By the disk array data checksum mode, RAID technology is divided into different levels (RAIDLevels), with different technical features, the reader can refer to the manual selection.

In order to better improve the purchase of hard disk i/o performance, recommend using RAID technology, according to the characteristics of the application, to be frequently access read-write hard drive into a RAID0 RAID1 and RAID5 or; at present, can be adopted at the low-end server, such as wave yingxin IDERAID NP200; while in the middle and high-end server, recommended SCSIRAID controller and RAID controller on technical indicators, such as the CPU type, channel type and number, number, there is no cache battery back-up, etc.; Note: motherboard integrated RAID controller because there is no hard disk controller, which uses the SCSI on motherboard, hard drive controllers take more primary processor time, causes the server's processing ability is affected.

Hot technology

In addition to the evaluation from the performance indicators on the purchase of hard drive, but also hard disk failure rate, average non-fault operation and easy maintenance. In the specific application, you first should use long life, low failure rate of the hard disk, you can reduce the probability of failure and the number of times, this involves hard disk MTBF (mean time between failures) and data protection technology, MTBF value better, such as wave yingxin servers hard disk MTBF values of more than 120 million hours in General, and the hard disk drive S.M.A.R.T. shared by (Self monitoring, analysis and reporting technology), and similar technologies, such as seagate and IBM DST (drive self test) and DFT (drive health detection), saved on your hard disk data safety is of great significance.

In addition, once the hard disk is damaged, you should consider how to ensure that data is not lost, and reduce server downtime. RAID technology can be used to ensure data reliability and security, through the hard disk of the hot technology can guarantee to replace or repair the hard disk at the same time, the server still runs correctly. Current hot technologies in the high-end server is very common, has also been used as an important server grade. General in the server's hot technology parts have hard drives, power supplies, fans, PCI slots, and SCSI hard drives also have a dedicated support hotplug technologies SCA2 interface (80-pin), and SCSI backplane, you can easily choose the hard disk of hot pluggable.